1. Field of the Invention
The present invention relates to a control device for an engine having an automatic stop and start function.
2. Description of the Related Art
Known in JP-A-4-246252 or the like is a vehicle having an engine automatic stop and start function in which the engine is automatically stopped when it goes into predetermined engine stopping conditions, and it is also automatically started when it goes into predetermined engine re-starting conditions. This technology has been developed to further promote the reduction of exhaust gas emissions and conservation of energy.
On the other hand, a thermostat is provided on a water-cooled engine which has a function to maintain the temperature of water in a water jacket within a predetermined range, and an abnormal operation of the thermostat invites a reduction of combustion efficiency attributed to improper engine temperatures, worse exhaust gas properties and fuel economy thereby resulting. Due to this, recently it is one of significant subjects in the field of engine control to find an abnormal state of the thermostat at an earlier stage.
Proposed as a means for finding an abnormal state of a thermostat at an earlier stage in, for example, JP-A-11-141337 is a system in which the quantity of intake air which is directly related to the total heat release value of an engine is accumulated since the engine is started and in which, when the accumulated value of the quantity of intake air has reached a predetermined value, an estimated cooling water temperature calculated based on a total heat release value of the engine estimated from the accumulated value on condition that the thermostat is in normal operation is compared with an actually measured cooling water temperature actually measured by a cooling water temperature sensor, whereby the thermostat is determined to be in an abnormal state when a deviation between the estimated cooling water temperature and the actually measured cooling water temperature exceeds a predetermined value.
In recent years, however, the combustion control of an engine which is related to the ignition timing or the quantity of injected fuel is generally controlled in an electronic fashion, and on suitable occasions data in a CPU installed in an electronic control unit (ECU) needs to be initialized and a self-diagnostic process also needs to be performed on the CPU on such occasions. Conventionally, it is common practice to execute the initialization of data and self-diagnostic process at the time of cranking.
However, in a case where an engine automatic stop and start function is applied to a vehicle equipped with the aforesaid thermostat proper operation determination function, since the CPU is initialized when the engine is re-started after it has been automatically stopped, there may be a risk of interrupting the thermostat proper operation determination based on an accumulated value of the quantity of intake air since the engine is initially started.
The present invention was made with a view to solving such a problem inherent in the related art, and an main object thereof is to provided a control device improved such that even if an automatic stop and start function is added to a vehicle, there is caused no risk of a thermostat proper operation determination device malfunctioning to make a wrong judgement
With a view to attaining the above object, according to aspects of the invention, there is provided a control device for an engine includeng an automatic stop and start function, wherein detected data taken prior to an engine stop or results of an operation carried out based on the detected data are retained in executing an engine automatic stop control. In particular, in a case where the technology is applied to an engine including a thermostat proper operation determination function, a thermostat proper operation determination process is constructed so as to continue to be executed during an engine automatic stop control.
According to the constructions, since the processes are jumped to be performed when the engine is initially started, the accumulated data for use in determining whether the thermostat is in proper operation does not have to be initialized.